Asystem consists of a copper tank whose mass is 13 kg, 4 kg of water, and an electrical resistor of negligible mass. the system is insulated on its outer surface. initially the temperature of the copper is 27°c and the temperature of the water is 50°c. eventually, the system comes to equilibrium at 45 c. "determine the work done"

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

i think the answer would be b

f=ma newton's second law 7x8=56n

no. dot product   =0 when vecs at right angles